Combined air exhauster and compressor



Nov 1957 G. L. COTTER 2,812,893

COMBINED AIR EXHAUSTER AND COMPRESSOR Filed June 28, 1954 George L .Co11er.

4W firm ATTORNEY United States Patent-O COMBINED AIR EXHAUSTER AN D COMPRESSOR George L; Cotter, Pittsburgh, Pa., assignor to Westinghouse Air Brake Company, Wilmerdiug,'Pa., a corporation'of Pennsylvania Application June 28, 1954, Serial No,,439,7 68

6 Claims: (Cl. 230-46) This invention relates to 'a combined air exhauster and compressor device, and more particularly to means for exhausting the clearance spacein the cylinder to atmosphere for increasing the efliciency of said combined 'device.

In the ordinary type ofcombined air exhauster and compressor, a piston is operative upon an intake stroke to draw fluid under pressure from a vacuum line through an inlet valve into a. compression chamber and upon a compression stroke to compress fluid under pressure admitted from the atmosphere to said compression chamber at the end of said intake stroke and force it through an outlet valve into a supply line. At the top dead center of the piston stroke there is a continuation of the compression chamber, commonly called the clearance space so that the piston at the completion of the compression stroke will not ram and damage the cylinder head. Now as the piston moves through its compression stroke and reaches top dead center, the clearance space will be charged with fluid under pressure. As the piston moves through its intake stroke, thereby enlarging the volume of the clearance space, the pressure "of fluid in the clearance space and compression chamber must be reduced below the pressure of fluidin the vacuum line. before fluid under pressure will flow into said compression chamber. The higher the pressure of fluid in the clear-- ance space the greater distance. the piston must travel through its intake stroke to reduce said pressure of fluid below that in the vacuum line. It is therefore seen that the full intake stroke of the piston is not used in drawing fluid under pressure from the vacuum line with a resulting loss in the operating efiiciency of the combined air exhauster and compressor.

The principal objectof the invention therefore is .to provide means for increasing the operating efliciency in the above type of device.

Another object of the invention is to provide means whereby the pressure of fluid inthe clearance space is exhausted to atmosphere prior to beginning of the intake stroke. 7

Other objects andadvantages of my invention will'be apparent from the detailed description given hereinafter when read in connection. with the accompanying drawing, in which the single figure is a diagrammatic view, mainly in section, of a combined air exhauster and compressor device embodying my invention.

Description For illustrative purposes only, my'invention is shown embodied in a single stage type combined air exhauster and compressor comprising a casing 1 havingsecured to the bottom surface thereof in a suitable manner the usual crankcase 2 in which is rotatably mounted the'usual driven crankshaft 3 which is operably connected through the medium of a rod 4 to a piston Sslidably mounted in a cylinder 6 for reciprocation by said crankshaft.

The cylinder 6 is closed at its upper end by. a cylinder 2,812,893 Patented Nov. 12, 1957 2 head 7 thereby defining with thewalls of said cylinder and the face side of piston 5 the usual compression chamber 8.

Extending vertically-through the left-hand side of the cylinder head 7 is an opening 9 which constitutes a part of a fluid inlet communication to the device and is closed at its upper end by a valve seat member 10 held in place by a retaining nut 11 which is secured to the device by a threaded locking cap nut 12. The locking cap nutl2makesscrew-threaded connection with the periphery of the retaining nut 11 and jams against the upper surface of the head-7 and thereby closes the upper endof an inlet chamber or cavity 13 which communicates by way of a port 14in the retaining nut 11 with an inlet pipe 15 and by way of ports 16 in the valve seat member 10'with'opening 9 and thereby chamber 8. Communication through ports 16 is controlled by an annular inlet valve 17 which is urged upwardly towards seating contact with valve seat member 10 by a spring 18 interposed between said seat member and a spring seat 19 secured to valve seat member 10 by screw-thread means 20.

In a somewhat similar manner an opening 21 at the right-hand side of'the cylinder head 7 for the exhaust or discharge communication is closed by a valve seat member 22 likewise held in place by a retaining nut 23 and a locking cap nut 24 corresponding to nuts 11 and 12, respectively. A discharge chamber or cavity 25 is connected to a discharge pipe 26 by way of a port 27 in the retaining nut 11 and may be-connected to compres sion chamber 8 by way of'ports 28 in the seat member 22. An annular discharge valve 29 is urged downwardly towards seating engagement with seat member 22 by a spring 30- interposed between said valve member and a spring seat 31 which ismounted on said seat member by screw-thread means 32.

I According to the invention, a'bore'33 is formed in the cylinder head 7 at-the topof-the chamber S in coaxial alignmentwith cylinder 6, in which chamber a valve seat member 34 is secured by screw-thread means 35 and locked by a cap'nut 36 which makes a screwthread connection with the outer periphery of said seat member and jams against the top surface of cylinder head 7. An upwardly facing, annular valve seat 37 is formed integrally of the valve seat member 34 for seating engagement with a relief valve 38 urged toward its seating, position by a spring 39 contained-in a chamber 40. The chamber 40is definedby seat member '34 and cap nut 36 and is constantly open to atmosphere by way ofa tubular sleeve 41, a port42, a chamber 43 anda pipe connection 44in said cap nut. The tubular sleeve 41 is pressed into cap nut 36, from which it extends downwardly into chamber 40 toprovide a guide for spring 39;

As hereinafter described, it is not intended that relief valve 38 be unseated by pressure of fluid in chamber8 but rather through direct. mechanical operation by a stud, or plunger, 45 secured in the center of the face of piston 5, and thereby in coaxial alignment with cylinder 6 and valve-seat member 34, upon'piston 5 reaching its upper dead center position and after discharge valve 29 has seated. It will be apparent, therefore, that the value of spring 39 "will be substantially in excess of that of spring 30;to insure the completed cycle of operation of exhaust valve 29 beforerelease valve '38 is unseated.

The wall of cylinder 6 is further provided with aplurality of inlet ports 46 protected by curledhair strainers 47, which ports are adapted to be fully uncovered by piston 5 upon reaching its lower dead center position.

. Operation In operation; whenthe crankshaft 3 is rotated. by any suitable source of power, piston will be reciprocated by the connecting rod 4, completing an inlet and discharge stroke for each revolution of the crankshaft.

Inthe accompanying drawing, piston 5 is shown in its lower dead center position, in which all valves will be in their seating positions, as shown, and fluid in chamber 8 will be opened to atmosphere through inlet ports 46. Upon rotation of crankshaft 3, connecting rod 4 and there by piston 5 will be actuated upwardly, the piston first cutting chamber 8 ofl from atmosphere by covering the mouths of the inlet ports 46. The piston 5 as it moves upwardly compresses the fluid in chamber 8 until the upwardly directed force exerted on the discharge valve 29 unseats the valve against the combined downwardly directed force exerted by the spring 30 and the fluid pressure which may exist in the discharge pipe 26. With valve 29 unseated fluid will flow from chamber 8 through ports 28 to discharge chamber or cavity 25, and thence through ports 27 into discharge pipe 26 and a suitable fluid receiver, not shown. Fluid under pressure will continue to flow in this manner until the piston 5 nearly reaches the end of its upward stroke when, with the fluid pressure in discharge pipe 26 and chamber 8 substantially equal, the force of spring 30 will prevail and valve 29 will again be seated thereby.

According to the invention, the continued upward movement of piston 5 after the discharge valve 29 has been seated will bring the stud, or plunger, 45 into contact with relief valve 38 and unseat it, whereupon the pressure of fluid remaining in the clearance space between piston 5 and cylinder head 7 in chamber 8 will flow through chamber 44 sleeve 41, port 42, chamber 43 and connection 44 to atmosphere, thus reducing the pressure in chamber 8 from receiver pressure to atmospheric pressure.

Initial movement of the piston 5 in a downward direction will carry plunger 45 out of contact with relief valve 38 and thereby permit spring 39 to again seat said valve. At this time valves 17 and 2.9 will both be seated as shown in the drawing. Additional downward movement of piston 5 after relief valve 38 has seated will bring the pressure of fluid in chamber 8 sufliciently below atmosphere to allow pressure of fluid in chamber or cavity 13 and connected vacuum pipe 15 to move valve 17 against the force of spring 18 and away from valve seat member 10. Fluid will then flow from a suitable vacuum storage means, not shown, through inlet pipe 15 to inlet chamber or cavity 13 by way of port 14 and thence through ports 16 in valve seat member to chamber 8. As the piston nears the end of its inlet, or suction, stroke the pressures in vacuum pipe and chamber 8 will be substantially equal and inlet valve 17 will again be seated by spring 18. However, in completing the inlet stroke piston 5 will again uncover inlet ports 46, allowing fluid at atmospheric pressure to flow to chamber 8 in readiness for the next compression stroke.

Piston 5 will now be at its lower dead center position as illustrated with the valves positioned as shown. The same operation will follow as just previously described.

Summary From the foregoing it will be seen that with this invention I have provided an improved exhauster and compressor device which is more eflicient by reason of a relief valve mechanically operated to reduce the pressure of fluid in a cylinder at the end of a compression stroke at atmospheric pressure before taking up a suction stroke and thereby effecting an earlier unseating of the inlet valve in the suction stroke operation to provide a longer more productive suction stroke.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a combined air exhauster and compressor, the combination of, a cylinder, a cylinder head secured to said cylinder, a piston reciprocable within said cylinder and forming with said head a combined vacuum and compression chamber therein, openings in said head, valves located in said openings and adapted to control communication with said chamber, a port located in the cylinder wall and adapted to be uncovered by said piston at the end of its exhausting stroke whereby said chamber is opened to atmosphere in preparation for the compression stroke, a normally closed relief valve located in said head controlling communication between said chamber and the atmosphere, and means carried by said piston adapted to open said relief valve at substantially the end of its compression stroke to exhaust compressed air from said chamber in preparation for the exhausting stroke.

2. In a combined air exhauster and compressor, the combination of, a cylinder, a head secured to said cylinder, a piston reciprocable within said cylinder and forming with said head a combined vacuum and compression chamber therein, inlet and exhaust openings in said head, valves located in said openings adapted to control the flow of fluid under pressure to and from said chamber, respectively, a port located in the cylinder wall and adapted to be uncovered by said piston at the end of its exhausting stroke whereby said chamber is opened to atmosphere in preparation for the compression stroke, a relief valve located in said head controlling communication between said chamber and the atmosphere, means carried by said piston operative to unseat said relief valve at substantially the end of its compression stroke to exhaust compressed air from said chamber in preparation for its exhausting stroke, and means for effecting the operation of the relief valve to its closed position at all other times.

3. In a combined air exhauster and compressor, the combination of, a cylinder, a head secured to said cylinder, a piston reciprocable within said cylinder and forming with said head a combined vacuum and compression chamber therein, inlet and exhaust openings located in said head, valves located in said openings adapted to control the flow of fluid under pressure to and from said chamber, respectively, a port located in the cylinder wall and adapted to be uncovered by said piston at the end of its exhausting stroke whereby said chamber is opened to atmosphere in preparation for the compression stroke, a

relief valve located in said head controlling communication between said chamber and the atmosphere, a plunger carried by said piston adapted to open said relief valve at substantially the end of its compression stroke to exhaust compressed air from said chamber in preparation for the exhausting stroke, and means for effecting the operation of the relief valve to its closed position at all other times.

4. In a combined air exhauster and compressor, the combination of, a cylinder, a cylinder head secured to said cylinder, a piston reciprocable within said cylinder and forming with said head a combined vacuum and compression chamber therein, openings in said head, valves located in said openings and adapted to control commuunication with said chamber, a port located in the cylinder wall and adapted to be uncovered by said piston at the end of its exhausting stroke whereby said chamber is opened to atmosphere in preparation for the compression stroke, a normally closed relief valve located in said head controlling communication between said chamber and the atmosphere, and means conditionable by the movement of said piston to the end of its compression stroke to momentarily open said relief valve.

5. In a combined air exhauster and compressor, the combination of, a cylinder, a head secured to said cylinder, a piston reciprocable within said cylinder and forming with said head a combined vacuum and compression chamber therein, inlet and exhaust openings in said head, valves located in said openings adapted to control the flow of fluid under pressure to and from said chamber, respectively, a port located in the cylinder wall and adapted to be uncovered by said piston at the end of its exhausting stroke whereby said chamber is opened to atmosphere in preparation for the compression stroke, a relief valve 10- cated in said head controlling communication between said chamber and the atmosphere, and means operative as of incident to the movement of said piston to the end of its compression stroke to open said relief valve and to actuate said valve means to close said communication at all other times.

6. In a combined air exhauster and compressor, the

combination of a cylinder, a head secured to said cylinder, a piston reciprocable within said cylinder and forming with said head a combined vacuum and compression chamber in said cylinder, a vacuum cavity in said head adapted to communicate with a space to be evacuated, a fluid pressure cavity in said head adapted to communicate with a space to be pressurized, an inlet valve located in said head for controlling communication between said chamber and said vacuum cavity, a discharge valve located in said head for controlling communication between said chamber and said fluid pressure cavity, a port located in the cylinder wall and adapted to be uncovered by said piston at the end of its exhausting stroke whereby said chamber is opened to the atmosphere in preparation for a compression stroke, a normally closed relief valve located in said head controlling communication between said chamber and the atmosphere, and means carried by said piston operative to unseat said relief valve at substantially the end of its compression stroke to exhaust compressed air from said chamber in preparation for an exhausting stroke.

References Cited in the file of this patent UNITED STATES PATENTS 1,688,889 Spreen Oct. 23, 1928 2,406,202 Crittenden Aug. 20, 1946 FOREIGN PATENTS 688,117 France Aug. 19, 1930 

